1. Field of the Invention
Apparatuses and methods of the present general inventive concept relate to a computer system and a control method thereof, and more particularly, to a computer system which inspects a defective cell in a memory, and a control method thereof.
2. Description of the Related Art
A conventional memory is used as a storage device in a computer system and has two types including a Random Access Memory (RAM) and a Read-Only Memory (ROM). RAM is generally used by a processor to read and write data, and is a typical volatile memory that loses stored data when the computer system powers off. ROM is used to store unchangeable data such as Basic Input/Output System (BIOS) and is a typical non-volatile memory that does not lose stored data when the computer system powers off.
Recently, there has been a trend to increase memory capacity. However, if only one of a plurality of cells in the memory becomes defective, the memory can become unavailable, thereby causing a whole system to be unavailable.
To prevent the foregoing problem, a conventional technology is disclosed in “System Memory Control Device,” Korean Patent First Publication No. 1999-032660, wherein a memory including a defective cell can be available by using a circuit to rearrange addresses in the memory.
More specifically, the conventional technology inspects a memory and stores an address of a memory which replaces an address of a defective cell of a memory or defective memory address. A central processing unit (CPU) checks whether an address of a memory to be accessed is a defective memory address. If the memory address is in fact defective, a memory address is rearranged so that the memory cell indicating the defective memory address indicates a memory cell which indicates a replacement memory address. Accordingly, a memory which includes the defective cell may be used.
However, in the conventional technology, the CPU checks whether a memory address to be accessed is a defective memory address whenever the CPU accesses a memory. Further, since a memory address is replaced with a replacement memory address, it takes lots of time to access the memory. Thus, a system may deteriorate in performance, and a memory with high capacity does not operate efficiently.
Also, an additional circuit is provided to rearrange a memory address, and since the circuit does not operate if there is no defective cell, excessive power consumption may occur.